1. Originally Posted by Syne
How do you expect a diameter to get smaller without the inner surface shrinking? $C=\pi\times d$, so if the diameter gets smaller then the circumference, which is the surface length of the hole, must get smaller as well.
Hi again, mate.

Sorry if I am not making myself clearer.

If the surface 'wrinkles', the surface may stay the same 'area' but its ridges effectively make the 'fitting space' smaller diameter without the actual inner surface area changing much.

Then I also said that the inner diameter may not change because the inner surface layers may be 'compressed' and made a denser layer than the material behind it.

That's all I meant mate. Cheers!

Disclaimer Again: I do not know about the 'heating fit' side of things. I've only ever used (once) the 'cooling' method for the stud/bolt to go into such a hole.

.

2. To All

I've said many times that I can find a video for any occasion. If you watch the following video you will know the answer and there won't be any doubts.

http://www.bing.com/videos/search?q=...ail&FORM=VIRE5

select the second video Conceptual physics Ball & Ring expansion

3. See my Post #8, where I suggested consideration of the circumference of both the inner & outer circles.

Isn't obvious that both circumferences expand as the washer is heated? If you think of the washer as made up of a large number of very thin rings, each ring would expand along the circumference.

If the inner circumference increases, the radius must increase.

I would expect the washer to get thicker (Id est: Difference between radii increases) with some expansion toward the center. I expect that expansion to be overwhelmed by the increase in circumference.

4. Originally Posted by Dinosaur
See my Post #8, where I suggested consideration of the circumference of both the inner & outer circles.

Isn't obvious that both circumferences expand as the washer is heated? If you think of the washer as made up of a large number of very thin rings, each ring would expand along the circumference.

If the inner circumference increases, the radius must increase.

I would expect the washer to get thicker (Id est: Difference between radii increases) with some expansion toward the center. I expect that expansion to be overwhelmed by the increase in circumference.
Maybe it would help to think of the hole as an arch that will dissipate any force directed towards the center around the circumference of the inner surface of the ring. Whatever, I like your example. I am somewhat surprised that so many people believed the hole would get smaller. Did anybody notice the difficulty rating on this problem was only 4 out of 10?

5. ...so if the washer was cut through on one side and the newly-cut edges were allowed to cross over (like a ribbon) then we could expect a shrinking hole?

6. Originally Posted by RJBeery
...so if the washer was cut through on one side and the newly-cut edges were allowed to cross over (like a ribbon) then we could expect a shrinking hole?
It's a good question.
I think whether it is cut or not, similar behave. As a photo enlargement.
Otherwise it would appear some very high tensions inside the material.
But this is only an opinion.

7. The material becomes molten before it expands by 1%?
The material puddles?
The hole decreases in the puddle?

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